Hydroponic and aeroponic production of medicinal crops in controlled environments provides opportunities for improving quality, purity, consistency, bioactivity, and biomass production on a commercial scale. Ideally, the goal is to optimize the environment and systems to maximize all five characteristics. Examples of crop production systems using perlite hydroponics, nutrient film technique (NFT), ebb and flow, and aeroponics were studied for various root, rhizome, and herb leaf crops. Biomass data comparing aeroponic vs. soilless culture or field grown production of burdock root (Arctium lappa), stinging nettles herb and rhizome (Urtica dioica), and yerba mansa root and rhizome (Anemopsis californica) are presented, as well as smaller scale projects observing ginger rhizome (Zingiber officinale) and skullcap herb (Scutellaria lateriflora). Phytochemical concentration of marker compounds for burdock and yerba mansa in different growing systems are presented.
Lettuce, Lactuca sativa L., plants were grown in soil irrigated at various intervals with nutrient solution and in hydroponics culture. Increased nutrient level added to the soil increased seed yield but did not give a corresponding increase in seedling performance.
Hydroponically propagated seed, although heavier than soil propagated seed, were relatively poor in vigor and germinability. A positive linear correlation was found between N levels (5-15 meq) and seed yield, weight per seed, and seedling vigor. Amounts of amino acids and lipids were not positively correlated with nutrient supply, N level, or seedling vigor. Lettuce seed weight was a useful parameter in predicting seedling vigor only within a seed lot obtained from plants grown under the same environmental and nutritional conditions.
Incidence of blossom-end rot (BER) of tomato is known to increase with increasing salinity in hydroponics and field tomato crops due to osmotic stress and imbalanced ionic ratio in the media solution. The present investigation evaluated salinity effects on the occurrence of BER of tomato in a completely closed root environment known as the closed insulated pallet system (CIPS). The CIPS is a continuous sub-irrigation capillary system with water moving from reservoir to rootzone in response to plant uptake and loss through transpiration and growth. In CIPS, fertilizer reserve is placed at the top surface of the root matrix, so fertilizer ions move downward by diffusion. Various tomato genotypes were seeded directly into CIPS in Spring. The experiment was terminated at a 100-day growing period. The incidence of BER was calculated as percent affected fruits. Salinity treatments consisted of five concentrations ranging from 0 to 10 g/L NaCl. One salinity treatment was 1 g/L CaCl2. In CIPS, the salt gradient created by uptake of saline water had lowest concentration at the top of root compartment where fertilizer was placed. Therefore, there was minimal ionic interactions between fertilizer ions and ions from the saline water. The uptake of water and plant growth decreased with increasing salinity concentration. The addition of Ca in the sub-irrigation water had no effect on the occurrence of BER. The incidence of BER correlated negatively with salinity level and plant growth in the CIPS.
Organosulfur compounds in onion extracts inhibit the aggregation of human blood platelets. Antiplatelet activity is important to human cardiovascular health. We hypothesized that modification of sulfur fertility may increase organosulfur compound concentration and thereby affect platelet inhibitory activity in onion. Four contrasting onion genotypes were grown at four sulfur levels in a hydroponic system in the greenhouse and in contrasting sulfur environments in seven field locations in Wisconsin, Oregon, and New York. The contrasting field sites were comprised of sandy soils with a mean sulfate level of 5.4 ppm and muck soils with a mean sulfate level of 20.3 ppm. Onions grown in field environments with increased soil sulfur concentrations had significantly higher antiplatelet activity (33% higher than sand-grown onions; P < 0.001). The greenhouse experiment was conducted in hydroponics with nutrient solutions containing four sulfur levels ranging from 0.8 mM to 15 mM sulfate. The 10-mM sulfur treatment resulted in onion bulbs with 10% higher antiplatelet activity over those grown in the 0.8-mM sulfur treatment (P < 0.06). These data suggest that sulfur concentration in nutrient solution and in soil may be directly responsible for the increased antiplatelet activity in onion extracts observed in this study.
The short time to flower and rapid production cycle of dwarf Brassica lines make it a promising candidate as an oilseed crop for NASA's Controlled Ecological Life Support Systems (CELSS) program. Breeding lines provided by Paul H. Williams are being screened at Purdue University for productivity and yield rate using soilless culture techniques under controlled-environment conditions. The small, irregularly-shaped Brassica seeds did not respond well to conventional methods of germination above the batch hydroponic systems, even when a variety of capillary ticking materials were used. At best, attaining uniformity of seedling stands required transplants, which compromised potential yield rates in terms of mechanical damage and inhibited seedling establishment. Present emphasis is on solid substrate soilless mixtures using passive ticking hydroponics systems. Crop growth rate, harvest index, and overall yield are being compared as a function of planting densities ranging from 117 to 1423 plants/m2 of growing area. Yield parameters are also being evaluated as a function of growth medium and level of ambient CO2 in the growth chamber atmosphere. Research sponsored by NASA Cooperative agreement NCC 2-100.
Limited-cluster production systems may be a useful strategy to increase crop production and profitability for the greenhouse tomato (Lycopersicon esculentum Mill). In this study, using an ebb-and-flood hydroponics system, we modified plant architecture and spacing and determined the effects on fruit yield and harvest index at two light levels. Single-cluster plants pruned to allow two leaves above the cluster had 25% higher fruit yields than did plants pruned directly above the cluster; this was due to an increase in fruit weight, not fruit number. Both fruit yield and harvest index were greater for all single-cluster plants at the higher light level because of increases in both fruit weight and fruit number. Fruit yield for two-cluster plants was 30% to 40% higher than for singlecluster plants, and there was little difference in the dates or length of the harvest period. Fruit yield for three-cluster plants was not significantly different from that of two-cluster plants; moreover, the harvest period was delayed by 5 days. Plant density (5.5, 7.4, 9.2 plants/m2) affected fruit yield/plant, but not fruit yield/unit area. Given the higher costs for materials and labor associated with higher plant densities, a two-cluster crop at 5.5 plants/m2 with two leaves above the cluster was the best of the production system strategies tested.
Maize (Zea mays) is increasingly grown in controlled environments to facilitate phenotypic analysis. Even with ample chelated iron (Fe), maize often develops interveinal chlorosis in soilless substrates or hydroponics because of inadequate bioavailable Fe in the plant. We hypothesized that the excessive phosphorus (P) in standard greenhouse fertigation solutions would accentuate the chlorosis. Here, we report that reducing the P concentration from 0.7 to 0.07 mmol·L−1 (22 to 2 mg·L−1) provided adequate P for rapid growth and increased chlorophyll concentration from 263 to 380 µmol·m−2. Restricted root-zones in containers require frequent watering and are often watered to excess, which flushes the root-zone with a high P solution. In a separate study, minimizing the leaching fraction increased leaf chlorophyll concentration from 123 to 508 µmol·m−2. The use of a ceramic substrate typically improves the green leaf color of maize plants. Consistent with this observation, we found no effect of high P concentration in the irrigation solution on growth or chlorophyll density in ceramic substrates because it strongly absorbs P from solution. These findings can significantly improve maize growth and nutrition in controlled environments.
Lettuce was produced using a new concept of hydroponics. The system is based on maintaining a constant water table (CWT). Plants grew on a flat surface and obtained the nutrient solution from capillary matting. One end of the mat was suspended in a trough containing the nutrient solution. The distance between the nutrient solution in the trough and the bench top was kept constant with a water level controller. The nutrient solution was resupplied from a larger reservoir. A ground cover on top of the capillary mat provided nutrient movement to the roots but prevented root penetration. Lettuce seedlings, germinated in small plug trays, were placed in holes cut in a 2.5-cm-thick styrofoam sheet. The styrofoam provided seedling support as well as protected the roots. Roots grew on the surface of the ground cover and were easily removed at harvest. The CWT could be adjusted by changing the height of the water level controller. The CWT concept of hydroponic production does not require pumps nor large storage reservoirs. No runoff occurs; the only nutrient solution used is that required by plants and a minimum amount of evaporation from the ground cover surface. Disease potential should be less than in other systems.
Water relation parameters were calculated from analysis of 92 pressure-volume isotherms of leaves of two olive varieties, `Leccino' and `Frantoio', measured after 4 weeks of salinity stress and 4 weeks of subsequent relief either in hydroponics or soil culture. `Frantoio' was more salt-tolerant than `Leccino', but no major differences in water relation parameters emerged between the two varieties. Increasing salinity from 0 to 200 mM NaCl decreased predawn leaf water potential from –0.5 MPa to –1.3 MPa, relative water content (RWC) from 97.6% to 89%, and leaf osmotic potential (Ψπ) from –2.0 to –3.5 MPa. Relative water content at turgor loss point (RWCtlp) was decreased from 89% to 85% (soil culture) and from 86% to 80% (hydroponic culture) in 0 to 200 mM CaCl-treated plants, respectively; a lower RWCtlp was also retained during the relief from salinity. Active osmotic adjustments induced by salinity was the result of accumulation of both inorganic ions and compatible solutes (e.g., mannitol). Maintenance of lower Ψπ and RWCtlp during relief indicated that salinized plants were better adapted to withstand further stress and that this potential might be exploited to harden olive plants to be used in arid or saline environments.
A container study and a hydroponics study were conducted to determine gas-exchange and ion content of `Cariflora' papaya plants as influenced by a combination of salinity and flooding. Plants grown in nutrient solution were subjected to 1 or 8 dS·m–1 as salinity treatments and 6.54, 3.62, or 0.92 mg oxygen/liter as the flooding treatments. Plants in the container study were subjected to 0, 4, or 8 dS·m–1 as salinity treatments, and half of the plants in each salinity level were flooded. Leaf gas-exchange began to decline by day 1 in all plants receiving flooding, and was zero by day 5. In contrast, gas-exchange of plants experiencing salinity began a slow decline after 5 to 7 days. Stomatal conductance of salinized plants was 25% to 33% of the control plants in the container study after 39 days. No interaction occurred between flooding and salinity treatments since the stomatal response to flooding was so rapid across all levels of salinity. Roots and stems played a major role in storing Na+ and Cl– in salinized plants. For example, stems contained more than two times the dry weight concentration of both ions as did leaves. Older leaves accumulated more Na+ and Cl– than did younger leaves. Flooding decreased Na+ and Cl– accumulation in roots, stems, and leaves in all salinized plants.